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Old 06-12-2013, 07:28 PM   #32
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Drives: 2012 Camaro RS, RX supercharged
Join Date: Dec 2009
Location: Bradenton, FL
Posts: 6,068
Originally Posted by 911medic View Post
If I'm using the wrong terminology, I apologize. The "reversion" I'm referring to can best be explained by this description I found online:
I'm not talking about PCV gases or oil reversion, I'm saying there's combustion reversion coming back onto the intake valves directly from the cylinder, as described above, possibly causing some of the deposits.

I am thoroughly convinced all of the oil in my manifold came in via the PCV system, and not via reversion (as I'm defining it).
Reversion occurs with every engine and the severity depends on the cam profile and is worse at high RPM's. In fact, if you search, there is a youtube video from 8-9 years ago showing an F1 car at WOT on a dyno and the reversion cloud of fuel is 2-3" above the injection stacks.

Most are not aware that reversion is also why when a valve drops in one cylinder (or other part failure) you commonly see parts and damage in most others from the reversion pulse throwing pieces back and forth.

On the exhaust ports on our big alky motors (.800 plus lift cam) we mill in antireversion grooves around each port to minimize the effect. It is also why if you have a vacuum gauge on your car at idle and deceleration you will see 18-22" plus of vacuum, but at WOT zero.

Excellent observation, but it has no effect on valve coking as any measurable amount of fuel would actually reduce the coking issue (top tier fuels like Shell, etc. on a port injection engine keep valves looking like new for 100K plus miles where a DI engine has no fuel passing or touching the intake valves).

Now, if you had a oil burner with wore out cylinder bores and rings you could see oil pushed back to the intake valves and the IM from reversion....but were talking relatively new engines on this forum, and the proof that adding a proper can like the RX, SM, or Elite when new, you find zero, or near zero deposits of any kind on the valves.

The oil is easy to see where it originates from by just looking in any catchcan and seeing as it is installed inline from the crankcase to the intake manifold. If it stops the oil then no oil will be present in the intake manifold itself (easy to see with a LLT...remove the plenum). Remove the can and see it coat with oil again.

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